2 questions to save space;) both non thirdgen "GM" 402 & 2.5
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From: Pueblo Co
Car: 1989 C4
Engine: L98
Transmission: 700r4
Axle/Gears: 307
2 questions to save space;) both non thirdgen "GM" 402 & 2.5
I'm building a BBC 402 for a 69 Camaro "I wish it was mine" will these heads "3964290"work for a 600hp aplication if ported?
(from MT.com).
...69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber Large or small hex spark plugs used.
Question 2. I'm working on a 86 Blazer 2.5 TBI, and it's surging badly at all speeds, No trouble codes show, fuel pressure is normal pump and filter are recent. It acts like you shifted from 1st to 4th gear and the battery light blinks when it starts to surge but the engine doesent die.
Thanks!
(from MT.com).
...69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber Large or small hex spark plugs used.
Question 2. I'm working on a 86 Blazer 2.5 TBI, and it's surging badly at all speeds, No trouble codes show, fuel pressure is normal pump and filter are recent. It acts like you shifted from 1st to 4th gear and the battery light blinks when it starts to surge but the engine doesent die.
Thanks!
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Joined: Sep 2001
Posts: 1,266
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From: Tallahassee, FL. USA
Car: 92 Camaro RS
Engine: 350 Crate Motor
Transmission: Tremec TKO
Axle/Gears: 10 Bolt 3.73
600 HP is going to be difficult with Oval Port heads,even new aftermarket aluminum ones.
Having only 402 cubes doesn't help either.
I have a 402 in a 70 Nova that puts out about 500 HP with Oval Ports. They've been ported and they're the later open chamber heads (119cc).
The early (closed chamber) heads you describe aren't bad, but the small combustion chambers tend to shroud the valves a little. It'll breath better with the open chamber heads.
Still, with the right cam, intake and carb, you should be able to get 450-500 HP out of a 402.
If you want more power than that you're gonna need rectangular port heads (the factory HP ratings for 396 motors were 325 and 350 with oval ports heads and 375(425 corvette) with rectangular ports and solid lifter cam).
Using a big solid cam (roller if you have the $), roller rockers, an 850 carb, single plane intake and rectangular port heads, you can make over 500 HP, but you'll need to spin it higher, maybe even use nitrous.
At those power levels , you better have a good steel crank and rods, forged pistons and a built TH400 with about 4000 stall.
A 12 bolt rear (or 9 inch) will be necissary as well.
Don't think I can help you with the 2.8 surging problem.
-Rich-
-Rich-
Having only 402 cubes doesn't help either.
I have a 402 in a 70 Nova that puts out about 500 HP with Oval Ports. They've been ported and they're the later open chamber heads (119cc).
The early (closed chamber) heads you describe aren't bad, but the small combustion chambers tend to shroud the valves a little. It'll breath better with the open chamber heads.
Still, with the right cam, intake and carb, you should be able to get 450-500 HP out of a 402.
If you want more power than that you're gonna need rectangular port heads (the factory HP ratings for 396 motors were 325 and 350 with oval ports heads and 375(425 corvette) with rectangular ports and solid lifter cam).
Using a big solid cam (roller if you have the $), roller rockers, an 850 carb, single plane intake and rectangular port heads, you can make over 500 HP, but you'll need to spin it higher, maybe even use nitrous.
At those power levels , you better have a good steel crank and rods, forged pistons and a built TH400 with about 4000 stall.
A 12 bolt rear (or 9 inch) will be necissary as well.
Don't think I can help you with the 2.8 surging problem.
-Rich-
-Rich-
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Well, doesn't his work out nicely for you? I wasn't going to be any more help on the BB 400 than nipples on a bull, but I may have some ideas on the 151.
Take a good look at teh EGR system on teh little engine. IIRC, the control is all mechanical (TVS instead of solenoid). I had the same problem on a 151 and found a TVS that was leaking through. The EGR would open to the point where intake vacuum would drop, nearly stalling the engine but closing the valve. The process would get cyclic, opening and closing every second or two depending on engine load.
Take a good look at teh EGR system on teh little engine. IIRC, the control is all mechanical (TVS instead of solenoid). I had the same problem on a 151 and found a TVS that was leaking through. The EGR would open to the point where intake vacuum would drop, nearly stalling the engine but closing the valve. The process would get cyclic, opening and closing every second or two depending on engine load.
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